In recent years, the use of a NiSi film in the salicide process as the gate electrode material is attracting attention. Compared to cobalt, nickel is characterized in that it is capable of forming a silicide film with less consumption of silicon in the salicide process. NiSi, as with a cobalt silicide film, is characterized in that the increase of fine wire resistance pursuant to the refinement of wiring is unlikely to occur.
In light of the above, nickel is being used instead of cobalt, which is expensive, as the gate electrode material. Nevertheless, NiSi tends to make a phase change to the more stable phase of NiSi2, and there is a problem of the degradation of the boundary roughness and increase in the resistance. And, there are other problems in that the clumping of the film and excessive formation of silicides may occur.
Conventionally, as a technique of using a Ni silicide film or the like, there is technology of capping and annealing a metal compound film made of TiN or the like on a Ni or Co film to prevent the formation of an insulation film as a result of reacting with oxygen upon forming the silicide film. Here, TiN is used to prevent the formation of an irregular insulation film caused by the reaction of oxygen and Ni.
If the irregularities are small, since the length from the NiSi film to the connection of the source/drain diffusion layer will be long, it is said that the junction leak can be suppressed. In addition, TiC, TiW, TiB, WB2, WC, BN, AlN, Mg3N2, CaN, Ge3N4, TaN, TbNi2, VB2, VC, ZrN, ZrB and the like are also disclosed as the cap film (refer to Patent Document 1).
Further, with conventional technology, problems have been indicated in that the NiSi formed on the substrate is easily oxidized among the silicide materials, large irregularities are formed on the boundary area of the NiSi film and the Si substrate, and a junction leak will occur.
Here, a proposal has been made for sputtering a TiN film as a cap film on the Ni film, and subjecting this to heat treatment so as to nitride the surface of the NiSi film. This aims to prevent the NiSi from oxidizing, and suppress the formation of irregularities. Nevertheless, since the nitride film on the NiSi formed by accumulating TiN on Ni is thin, there is a problem in that it is difficult to maintain the barrier properties for a long period of time.
Thus, a proposal has been made of forming the silicide film under a mixed gas (2.5 to 10%) atmosphere with nitrogen gas added thereto so that the roughness of the silicide film will be 40 nm or less, and the grain size will be 200 nm or more. Here, it is desirable to cap one among Ti, W, TiNx and WNx on Ni.
Here, it is also possible to sputter Ni with only argon gas that does not contain nitrogen gas, subsequently sputter the cap film made of TiN, and thereafter inject N ions into the Ni film in order to add N in the Ni film (refer to Patent Document 2).
As conventional technology, a semiconductor device and its manufacturing method are disclosed, and the combination of primary metals of Co, Ni, Pt or Pd and secondary metals of Ti, Zr, Hf, V, Nb, Ta or Cr is described. In the Examples, the Co—Ti combination is used.
Cobalt has a lower capability of reducing the silicon oxide film in comparison to titanium, and the silicide reaction will be inhibited if there is a natural oxide film existing on the silicon substrate or the polysilicon film surface upon accumulating cobalt. The heat resistance properties are inferior to a titanium silicide film, and problems have been indicated in that the heat upon accumulating the silicon oxide film as the interlayer film after the completion of the salicide process causes the clumping of the cobalt disilicide (CoSi2) film and the resistance to increase (refer to Patent Document 3).
Further, as conventional technology, there is disclosure of a “manufacturing method of a semiconductor device”, and technology is described where an amorphous alloy layer with a metal selected from a group consisting of titanium, zirconium, tantalum, molybdenum, niobium, hafnium, and tungsten is deposited on a surface as a layer containing cobalt Co or nickel Ni in order to prevent the short-circuit caused by the overgrowth upon forming salicide. Here, although there are Examples that show a cobalt content of 50 to 75 at % and Ni 40/Zr 60, the alloy content is large for achieving an amorphous layer (refer to Patent Document 4).
The disclosed conventional technologies described above relate to the deposition process, and do not relate to a sputtering target. Further, with the conventional high purity nickel, the purity was roughly up to 4N excluding gas components, and the oxygen content was high at roughly 100 ppm. As a result of manufacturing a Ni alloy target based on this kind of conventional nickel, plastic workability was inferior and it was not possible to manufacture a high quality target. Also, there was a problem in that numerous particles were generated during sputtering, and the uniformity was inferior.
In light of the foregoing problems of the gate electrode material, the present Applicant developed a nickel-based sputtering target material doped with titanium or platinum as a particularly superior material, and proposed the inhibition of the phase change to the stable phase of NiSi2 (refer to Patent Document 5, Patent Document 6, Patent Document 7, and Patent Document 8).
Among the foregoing proposals, platinum-doped Ni alloy was the most effective, and had high effect at the time it was proposed. However, in recent years, reduction in the wiring width and increase in the processing temperature are becoming unavoidable, and thermal stability at even higher temperatures is being demanded. The Patent Document 8 improved the foregoing point and comprises the characteristic features of this point, and it can be said that the characteristics and usefulness of the Pt-doped Ni alloy of Patent Document 8 are exceptional.
Meanwhile, a platinum-doped Ni alloy (Ni—Pt alloy) entails the following problems; namely, platinum is expensive, and, when used as a sputtering target, the sputtering characteristics are inferior since it possesses high magnetic permeability. Since a target with magnetic permeability has a low pass-through flux (PTF), magnetic field lines are locally concentrated on the surface of the target during sputtering and the erosion area of the target tends to be small.
Thus, as the erosion progresses, the difference between the portion where erosion is selectively advanced and the portion where erosion does not advance as much will increase. Then, the variance in the thickness of the target will arise. Since the most eroded portion becomes the duration of life of the target, there is a problem in that the usability will considerably deteriorate. Moreover, since the changes in the shape of the eroded portion will become remarkable, there is a possibility that the uniformity of the sputtered film will also be affected. Thus, as a Ni alloy target that is effective in forming a Ni silicide film, demanded is a material with the lowest possible magnetic permeability; that is, with a high pass-through flux (PTF).
Nickel is a typical material with high magnetic permeability, and the magnetic permeability will decrease slightly as a result of adding platinum to nickel. Nevertheless, it cannot be said that this is a material with the lowest possible magnetic permeability and a high pass-through flux (PTF) as the Ni alloy target as described above.
In addition to foregoing Patent Documents 1 to 8, as conventional technology, there are other documents such as the following Patent Documents 9 to 17 which describe technologies based on a Ni alloy. For example, Patent Document 9 describes a Pt—Ni alloy target, Patent Documents 10 to 13 describe a nickel silicide sintered compact target, Patent Document 14 describes a Ni alloy target in which silicon is solutionized, Patent Document 15 describes a Ni—Si alloy target, Patent Document 16 describes a high purity Ni alloy target, and Patent Document 17 describes a Ti—Cu—Ni alloy target, but none of these documents are able to resolve the foregoing problems to obtain a nickel-platinum alloy having superior characteristics.    [Patent Document 1] Japanese Unexamined Patent Application Publication No. H7-38104    [Patent Document 2] Japanese Unexamined Patent Application Publication No. H9-153616    [Patent Document 3] Japanese Unexamined Patent Application Publication No. H11-204791 (U.S. Pat. No. 5,989,988)    [Patent Document 4] Japanese Unexamined Patent Application Publication No. H5-94966    [Patent Document 5] Japanese Unexamined Patent Application Publication No. 2003-213405    [Patent Document 6] Japanese Unexamined Patent Application Publication No. 2003-213406    [Patent Document 7] WO2005-083138    [Patent Document 8] Japanese Unexamined Patent Application Publication No. 2009-167530    [Patent Document 9] Japanese Unexamined Patent Application Publication No. S63-335563    [Patent Document 10] Japanese Unexamined Patent Application Publication No. H8-144053    [Patent Document 11] Japanese Unexamined Patent Application Publication No. H8-144054    [Patent Document 12] Japanese Unexamined Patent Application Publication No. H8-144055    [Patent Document 13] Japanese Unexamined Patent Application Publication No. H8-67972    [Patent Document 14] Japanese Unexamined Patent Application Publication No. H10-251848    [Patent Document 15] Japanese Unexamined Patent Application Publication, Translation of PCT Application No. 2001-523767    [Patent Document 16] Japanese Unexamined Patent Application Publication No. 2003-213407    [Patent Document 17] Japanese Unexamined Patent Application Publication No. 2005-171341